DESCRIPTION: (Applicant's Description) Little is known about the process by which nicotine dependence develops among adolescent tobacco users. This project will follow a cohort of 650 7th grade students over a period of three and one half years. These subjects will be interviewed every four months during this period about their experiences with tobacco. The tobacco use of these subjects will be monitored in detail with specific attention to the duration of use, the frequency of use and the amount of tobacco consumed. Subjects will be monitored for the development of symptoms of nicotine dependence. The following specific hypotheses will be addressed: 1) Symptoms of nicotine dependence can appear within two months of the first use of tobacco. 2) Symptoms of nicotine dependence can be present when consumption averages less than one cigarette per day. 3) Youths can develop symptoms of nicotine dependence prior to the onset of the daily use of tobacco. 4) The inability to refrain from smoking where it is prohibited will not be an early symptom of dependence.